Logic Masters Deutschland e.V.

Set for Scojo's Setting Saturdays. The prompt was Mad Fold-In. You can find more Mad Fold-In puzzles here:
https://logic-masters.de/Raetselportal/Suche/erweitert.php?skname=x&sktext=x&suchtext=Fold-in

• Standard sudoku rules apply. The digits 1 through 9 appear in every row, column, and box.
• Mad Fold-In. If the cells between the dashed columns are removed, all clues fold into valid clues in the resulting 4x9 grid.
• Each question mark represents some number, to be determined by the solver. The value of a question mark doesn't change when folding.
• Cage Sums. Digits in a cage add to the total in the top left corner of the cage. Digits cannot repeat in cages.
• Diagonal Sums. An arrow clue outside the grid gives the sum of the digits along the indicated diagonal. Digits may repeat if allowed by other rules.
• X-Sums. An X-sum clue outside the grid gives the sum of the first X numbers placed in the corresponding row or column, where X is digit in the cell next to the X-sum clue. X can not be larger than the number of cells in that row or column.

Play in SudokuPad

Thank you to Cirne for testsolving, feedback on puzzle visuals, helping me come up with the title, and CSS.